Sanding and Finishing MDF

      How much sanding is involved in getting a nice finish on MDF? September 29, 2009

I am wondering what other folks are charging for painted finishes. We use an outside finisher who charges $12.00/ft for a painted finish. This is a satin, opaque pre-cat lacquer finish on MDF. That adds up quickly, but in addition, our finish materials supplier tells us that the only way to get a really good finish on MDF is to sand it to 400g. We spend a huge amount of time sanding; 150,220,280,320,400g. No wide belt, only 6' Festool R/O sanders. Any suggestions on how to lower the cost and still get a top notch finish?

Forum Responses
(Finishing Forum)
From contributor A:
What are you sanding? Routed panels or other machined areas of the MDF or the factory flat surfaces? What does your finisher say about the sanding?

From the original questioner:
Everything is flat slabs. We are switching over to a new finisher and I have not yet been able to pin him down on exactly how he would want the parts prepared. It could be that he does not require sanding to 400g. The bigger question is what do I need to do to get the best finish, and how much can I expect that to cost. My old finisher charged $7.50/ft, but the quality was not there.

From contributor B:
The flat unmachined panels should not be sanded at all. The machined or abraded areas should be sanded to 240, spot primed, then sanded to 320 and then primed. Sanding any substrate past 240 is a fool's errand. The primer may have adhesion problems. Primer is a hell of a lot easier to sand than wood or MDF.

Glass finish on a sheet of MDF:

do not sand(this is your prep work)
spray 1st coat primer
sand 320
spray 2nd coat primer
sand 400
spray 1st top coat
sand 400
spray 2nd top coat

Find a new finisher.

From contributor C:
You shouldn't have to sand beyond 220 grit. The nice sanding is on the primer. You need a good high build primer and he needs to let it dry thoroughly. That will eliminate a lot of the sanding scratches that can telegraph through.

From contributor D:
We burnish rather than sand routed areas with 400g. There is little to no sanding on-non machined areas. Prime with MLC Level and coat with MLC Stealth. This is a great finish for MDF. When you say $12.00/foot, are you talking running foot of cabinet, square foot of finish or what?

From the original questioner:
$12.00 sq/ft (1 side, double for 2 sided)

From contributor E:
Finishing costs vary just like the quality of a finish can vary. Simply because someone may charge a pretty penny does not necessarily mean that you will get a perfectly shiny penny in return. More important is the consistency of the finish that you get from the finisher, his/her ability to meet the schedule that you have set, his/her skill at finishing the particular project, etc...

I would not just judge a finisher by his/her cost for the job but by a few of the other aspects of finishing that I mentioned. I personally think that sanding an MDF panel or for that matter anything to 400 grit is overkill and as others have mentioned it could cause an adhesion problem, either right away ,or down the road when the finish has completely cured.

I can't say one way or another if you are paying too much money to have your cabinets finished but as a seasoned finisher myself I can say that quality coatings cost, quality finishes cost, and the satisfaction that you can rely on your finisher to come to bat for you each and every time you need him/her to also costs. Good finishers are hard to come by and once you find one, please do all you can to keep him happy because a good finisher is out to please the hand that feeds him.

From contributor F:
Here's my schedule Lou:
Sand MDF with 100
1 coat Clawlock
Sand with 180
1 more coat of Clawlock
Sand with 220
1 coat Resistant
Sand with 320
Last coat Resistant

If I need a gloss finish, I use 500 Abralon after the 320 sanding.

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Finishing

  • KnowledgeBase: Finishing: General Wood Finishing

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2020 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article